A review: dew water collection from radiative passive collectors to recent developments of active collectors

Abstract

Dew water is water droplets formed due to condensation of atmospheric water vapor on surfaces of temperature below its dew point temperature. Dew water can be seen as a nonconventional source of water and may be exploited in regions where weather conditions favor dew formation and inadequate supply and quality of water is a prevalent problem. There are two main types of dew condenser, the apparatus used to collect dew water, namely radiative (also called passive) and active condensers. Radiative passive collectors rely on exploiting the physical processes responsible for dew formation to collect dew water without any additional energy input. Previous studies indicate that a 1 m 2 radiative condenser yields between 0.3 and 0.6 L/day of dew water in arid and semi-arid regions. Active condensers have been designed as an alternative method of collection that produces higher yields by using additional energy inputs. Several designs of active condensers have been patented for which the yield can reach 20 L/day for portable devices, and up to 200,000 L/day for larger agricultural water devices. Active condensers are also known as atmospheric water generators, dehumidifiers, and air to water devices. Most of the active condensers are based on a regenerative desiccant that attracts and holds large volumes of water from the air or on a means of cooling the condensing surface below the dew point temperature (refrigeration circuit). The larger yields and wider range of environmental conditions in which dew can be collected make active condensers a promising option as an alternative or supplemental source of water in water scarce regions. The aim of this paper was to provide a comprehensive review of radiative and active condensers, including dew formation processes, methods of dew collection, and parameters that influence the dew collection. Subsequently, patents of active condensers were reviewed to ascertain how they can be integrated with different types of renewable energy and to assess the potential use of such integrated systems as a sustainable source of water in regions that suffer water scarcity and/or as a sustainable source of water for agriculture.

An Interfacial Solar‐Driven Atmospheric Water Generator Based on a Liquid Sorbent with Simultaneous Adsorption–Desorption

“…With increasing population and degrading environment, freshwater scarcity is becoming a major global challenge . As atmospheric water is estimated to be ≈10% of all fresh water on earth, water harvesting from air is attracting significant attention with several strategies such as fog water capture and dewing collection . Recently, solar‐driven atmospheric water generator based on a sequential adsorption–desorption process is emerging as a promising option.…”

Fog and Dew as Potable Water Resources: Maximizing Harvesting Potential and Water Quality Concerns

“…GeoHealth fog and dew harvesting projects are rarely implemented concurrently and yet both aim to ameliorate water scarcity. It is thus no surprise that despite the many fog and dew reviews (Fessehaye et al, 2014;Khalil et al, 2015;Klemm et al, 2012;Tomaszkiewicz et al, 2015), there has not been a single review that addresses the potability of fog and dew in the same paper. Assuming physical water scarcity and fog harvesting being a viable option, rain harvesting would be a logical extension (Wang & D'Odorico, 2008).…”

Dew, Fog and Rain Collector in a Hyper-arid Climate: Case Study in Abu Dhabi

“…The dew formation is notable during nighttime with a clear sky due to high radiant heat loss from the exposed surface. When the warmer moist air pass over the cool surface, the air is cooled and the water vapor condense into droplets on the surfaces [2]. Dew collectors can collect not only dew but also rain water.…”

“…There are two types of dew water collectors: radiative (passive) and active dew water condensers. Radiative condensers rely on collecting dew water via radiative exchange with sky which results zero energy input [2]. Dew collectors have been placed upon the sloped roofs of the buildings, terraces, and directly on the ground [3][4][5][6].…”